Magnetic flux transfer in core systems



Dec. 29, 1964 D. c. ENGELBART MAGNETIC FLUX TRANSFER IN CORE SYSTEMS 3 Sheets-Sheet 1 Filed O01. 30, 1959 Dec 29 1964 D. c. ENGELBART MAGNETIC FLUX TRANSFER IN CORE SYSTEMS Filed oct. so, 1959 5 Sheets-Sheet 2 n v n a Dec. 29, 1964 D. c. ENGELBART 3,163,854

MAGNETIC FLUX TRANSFER IN CORE SYSTEMS Filed Oct. 30, 1959 3 Sheets-Sheet 3 lady.

maan; @fn/@fumer IN VEN TOR.

BY wfw United States Patent Office Patented Esc. 29, 1964 3,l63,854 c IVAGNETIC FLUX TRANSFER El @GRE Douglas C. Engelbert, lialo Alto, tlaiif., assignor to AMP incorporated, Harrisburg, Pa., a corporation of New Jersey Filed Get. 36, 1959, Ser. No. 849,776 ti Claims. (Cl. 36in- 7174) This invention relates to mangetic-core systems of the type wherein data is transferred by transferring the state of magnetic remanence from one coreto another. More particularly, this invention relates to improvements in such systems whereby operating tolerances are broadened.

in an article entitled A High-Speed Logic System Using Magnetic Elements and Connecting Wire Gnly, by H. D. Crane, in The Proceedings of the LRE., Volume 47, pp. 6.3-73, January i959, there is described a shift register which employs magnetic cores for the bistable# state storage elements in the register. These cores are of a type commonly known as multi-aperture cores, in that they are substantially toro'idal in shape and have a large, central main aperture with at least two smaller apertures in the arms of the toroid. One of these smaller apertures is known as the receive aperture and the other is known as the transmit aperture. This shift register exemplies a type of device in which this invention is applicable. The shift register operates by virtue of initially receiving data in binary form, which is represented by certain ones of the cores in the register by the state of the magnetic remanence of these cores. For readout or delay purposes, the data in the shift register is shifted through the register, in theV course of which a core will transfer its'state of magnetic remanence to a succeeding core, in order that succeedingy core represent the bitof ,data stored in the transferring core.

The mechanics of the transfer from one core to another in a shift register, whereby the remanence flux states are transferred, are clearly explained in the previously mentioned article. aperture of one core is coupled to the receive aperture of a succeeding core through a closed-loop winding for the purpose of securing the transfer of flux from the one core to the succeeding core, A transfer current is applied to the closed-loop winding for the purpose of securing the transfer f liux from the one core to the succeeding core. This current has a value suchthat if the one core is in its zero state of magnetic remanence, the current flowing in the transfer winding does not affect the lstate of remanence of the succeeding core. However, if the one core is in a one-state of magnetic remanence, then the application of transfer current causes ux to switch about the transmit aperture, inducing'a Voltage in the transfer winding whereby a large part of the transfer current is steered through the receive aperture of the succeeding core, thereby driving it to its onestate of magnetic remanence. f

It will be appreciated from the above brief description of the transfer mechanism that a characteristic is required whereby for certain values of transfer current below a Ythreshold value the succeedingcore be 'unaffected and for values of transfer current above a threshold value, the succeeding core be driven to its one-state of magnetic remanence. This requires a flux transfer vcharacteristic Brieily, however, the transmitV `coupled to said transfer winding.-

An object of this invention is to provide an arrangement for optimizing the transfer characteristic between magnetic cores employed inv apparatus ofthe type de scribed. j

Another object of the present invention is to provide an arrangement in apparatus of the type described whereby there is considerable design latitude, while maintaining an optimum transfer characteristic 'between cores ernployed in the apparatus.

Yet another object of the present invention is the provision of a novel and improved arrangement for transferring llux and thereby the state of magnetic remanence from one magnetic core to a 'succeeding magnetic core.

These and other objects of the invention are achieved in a system of the type wherein itis desired to transfer the state ofmagnetic remanence of a first magnetic core to a second magnetic core by applying current to a transfer Winding coupling said first and second cores. Additional magnetic material'is provided which Iis inductively netic material has the property that it is drivable to a state of magnetic remanence before said second 'core'cani be driven'to `its state of magnetic remanence by the transfer current in said transfer winding. The additional magnetic material eifectively operates to remove liux sought to be transferred from the lirst to the second cores.

Thereby, an optimum transfer characteristic is effectuobjects Vand advantages thereof, willV best ibe understood from the following description when read in connection with the accompanying drawings, in which:v

FGURE V1 showsv an embodimentrof the invention api plied to a shift register employing a multiaperture magwhich is somewhat dihicult to achieve in practice, since can employ the embodiment of the invention, there is.-

shown in FIGURE l two stages of a shift register emf ploying multi-aperture cores. This should not be construed as a limitation upon the invention, sincerit will become apparent'that the inventive concepts areapplicale to arrangements lwherein it is desired to transfer flux from one core to a. succeeding core. The extension-of the principles to be described, to a shift register having any number of stages, will become apparent as lthis 'explana-v tion progresses. in the magnetic core shift register showrni there -e two cores required for storing each binary bit .of data. .The cores are numbered in sequence,jrespectively. il, i2, i3, and lli. One `stage of the register will include cores lliv and 12, andthe second stage of the register will include cores 13 andA i4. Each one of the cores will have a main aperture, respectively 11M, 12M, lh/l, and 14M, a receive aperture, respectively 11R, lZi, 13R, and idR, and a transmit aperture, respectively lil, EET, lST, and 314i". v Y To r'restoreallV the cores bearing cdd numbers in the' sequence or" cores to their ,clear state, there is provided a i clear-odd winding Ztl, which is Vinductively coupled to all the aforesaid cores throughV their main apertures. Current applied to the clear-odd winding serves the'function of restoring all odd-numbered cores to their cleared, or zero, state, A clear-even winding 22 is provided,

which serves thesame function for all the even-numberedV Said additional mag.

cores in the sequence of cores in the shift register. The clear-even winding 22 is coupled to all these even-numbered cores by their main apertures.

The transmit apertureof each core is coupled tothe 'receive aperture of a succeeding core by means of a transfer winding. The transfer windings for the arrangement shown in FIGURE 1 respectively are numbered 24, 26, 28. Transfer winding 24 couples cores 11 and 12; transfer winding 26 couples cores 12 and 13; and transfer winding 28 couples cores 13 and 14. In order to cause an advance of data from the cores `bearing odd numbers to the cores bearing even numbers, current is applied to the drive windings that are associated with the transfer windings which couple the odd-numbered to the evennumbered cores. The means of applying this current may be either direct, that is, by actually `connecting a conductor from a current source by means of a drive winding to the transfer winding between each of the odd and even cores, or in a preferred manner by inducing the required transfer current in the transfer loop. The arrangement shown in FIGURE l is `the'one for applying transfer current by inducing it.

An advance-odd-to-even winding 3th is threaded through the transmit aperture'llT and then through the mainy aperture, and back through the transmit aperture once again. It then is passed through the receive aperture 12R Vview of the transformer lcoupling with the transfer winding, induces a transfer current in the respective transfer windings 24, 26, 28, whereby a transfer or" fluxbetween the odd and even'cores may be effectuated.

An advance-even-to-odd winding 32 is also provided, and this couples to the transmit aperture 12T of the even core 12 and theV receive aperture 13R of the odd core 413 in the same manner as has been described for the coupling of the advance-odd-to-even winding 30 to the apertures 11T, 12R of the respective odd and even cores 11 and 12. The advance-even-to-odd winding in this manner is coupled to all the transmit and receive apertures ofthe respective even and odd cores in the shift register. Upon the application of a current to the advanceeven-to-odd winding, it induces currents in the transfer loops coupling the even and odd cores, whereby a transfer of ux between the cores may be eifectuated.

When advance current flows through the advance windtiux will beswitched about the transmit aperture only if the core were-in the one state. Otherwise, if the core were in the zero state, no liux would be switched in the transmittingr core, and no currents would be induced thereby in the transfer winding loop. The receiving core,

with no current in the transfer windings, will not switch either, and thus stays in the clear or zero state. l Y

If the transmitting core had been in the one state, the

advance current would cause switching about' its transmit ings of a core from which information is to be transferred, Y

aperture, and the transfer-winding current thereby in-H duced, when flowing through the receive aperture of the receiving core, adds to the of the advance-winding current there to cause switching ,of ux aboutthe main aperture of the receiving core. `lt may thus be stated aV state of remanence has been etfect'uated. Y

Inraccordance with this invention, extra magnetic material in theV form of small cores 4l, 42, 43 are coupled in ing-loop type of coupling to the transfer coil as shown,

that a transfer of iux has occurred orthata transfer of y there will be current in the transfer winding only during the time that flux linkages are being transmitted from the transmit to the driven. core. Assuming that each extra core i-, 42, 43 has a very low switching threshold and is initially saturated in the clear state, and is coupled to the transfer winding in a manner so that any current in the transfer winding which tends to drive the driven core toward the set state, will also drive this additional core toward its set state. The additional core thus will absorb most of the initial drive or ilux linkages which are sought to be transferred. This requires a relatively low transfer-winding loop current, assumedly low enoughso that very little Orino flux linkages are absorbed by the succeeding core until after the extra core is saturated. If flux linkages are still being injected into the transfer-winding loop after the extra core becomes saturated, then the loop current will increase to a limit (ideally) of twice the current being applied to the advance Winding. This increase causes the succeeding core to switch ever more rapidly after it begins to switch, and thereby the loop current will find an equilibrium value at which the driving and driven core are delivering and receiving, respectively, ux linkages at the same rate. It must be assumed that-the ratio of the number of turns through the transmit aperture of a core to the number of turns through the receive aperture of the succeednig core isl large enough so that the loss of iiux from the transmitted flux linkage leaves enough to set a significant amount into the driven core.

lt should be noted that the clear-odd winding 20 is also inductiveiy coupled to the magnetic cores 41 and 43 so that when the odd-numbered cores in the sequence are cleared these extra cores are also driven to their cleared state. Similarly, the clear-even winding 22 is also coupled to the aperture of extra core 42Yso that when the evennumbered cores in the register are driven to their clear state the even-numbered extra cores are also driven to their clear state. The operation of a shift register of the typeshown in FIGURE l requires that after each energi- `zation of an advance Winding, a clear winding is energized which clears the cores from which data has just been transferred. Thereby, the extra cores are cleared as well.

For the purpose of making an ideal analysis of the benets obtained in accordance with this invention and for implifying a consideration thereof, the effects of the transfer-Winding resistance and inductance upon a transfer operation should be neglected as well as the fact that a driven core is being switched slowly during the time before the extra core saturates. Assume, further, that all the volt seconds of flux linkage (in the absence of the extra core) issuing from the driving core will be absorbed in the driven core.

ln a completely lossless transfer situation without an extray core, there will he switched into a driven core an amount of tiux (pRzq received), which differs from that switched at the transmitting aperture of the driving core (T=q transmittedyby a factor of NT NR This impliesa constant value of flux gain, which could not satisfy the requirementsof thedigital technique here being develoeed. lf two different values of flux (i.e., flux switched away from the reference saturation direction) are desired to 'be transmitted stably from one multi-aperture core `to a second multi-aperture core, then there must exist a peculiar gbR vs. rpT curve, for which there are exact- 1yA two pointswhere unity gain exists and where ps 3 is less than unity; i.e., the ratio of the changein received flux divided by the change in the transmitted ux is less than unity.

FIGURE 2 is a graph of the relationship between gbR and T for the various cases to be discussed. The dotted line 50 illustrates a unity-gain curve. The line 52 illustrates a lossless case, where the ratio Nr l is greater than unity. Since it is not possible to transmit less than zero 1iux or to receive more than saturation ux, it is known that the iiux-gain characteristic must lie with'- in the ordinate range of from zero to saturation of a driven core, As a result, where a transmit-receive system has the characteristics designated by the curve 52, there would be only one stable point on the curve which would occur` when a driven core is at saturation. This can be considered so since the core would not long stay in a 'Zero' state in view of the existence of small perturbations which always occur in a practical system. The zero ux state is one of unstable equilibrium.

If a xed loss is introduced into an otherwise lossless' Since less than zero flux can never state of the core into a less-than-unity-gain range of the curve, which results in the ux level being forced back toward Zero during successive transfer operations. The Zero point on the curve is now one of stable equilibrium. Any initial state between the points zero, designated asa and pointV b on the abscissa, will result in the less-thanunity-gain characteristic existing inthis range, forcing the level down toward the stable zero flux state during successive transfer operations. Point b is 'the value of the ordinate at the crossover of the` curves Stb and 54 between zero ilux and saturation.

Any initial state between the points b and c will rind the more-than-unity-gain characteristic whereby the iiux level is forced up during successive transfer operations toward the upper equilibrium level, corresponding to point c. Any negative perturbations of the system superimposed upon the level at point c. would not alter the equilibrium level conditioner" the system.

An initial state corresponding to point b would not rind equilibrium. A positive perturbation would put the system into the greater-than-unity-gain range, driving the receiving core toward point c. A negative perturbation would put the system into a less-than-unity-gain range, whereby the receiving core would go baclr toward point a. Thus, point b is one of unstable equilibrium.

From actual operating experience with the multiaperturercore transfer systems, it has been found that in order to operate they must have the type of curve or characteristic designated by reference numeral 5d in FEGURE 2.

AAs was described previously, inthe case of a transfer VoperationV Vwhere the transmitting core is in the' zero'ilux state, there is current induced in thetransfer winding which circulates therein. .With a characteristic ofthe type represented by 52 in FIGURE 2, the receiving core would be driven partially toward its one state, regardless of whether or not the transmitting corewas in a one state. However, with the characteristic represented by S4 in FIGURE 2, a critical value of the drive must be exceede'dbefore the receiving core can'b'e driven toward its one state. l This situation where it is desired to use the multiaperture cores for transferring the state of remanence therebetween by ux transfer, the actual shape-of the curve for the system depends upon the interaction of a number of factors, such as advance-current amplitude and duration, transfer winding resistance and inductance, and the peculiar dynamic switching characteristics of the magnetic materials from which the cores are made. Freedomto manipulate these factors to the point where an optimum-shape flux-transfer curve may be obtained is not always present. In accordance with this invention, the introduction of the extra magnetic material as embodied in FIGURE l in the form of an extra core gives considerably more freedom in the L design of theother factors involved, so that the increased operational tolerances associated with a more optimumH curve, exemplified in FIGURE 2, can be realized.

. Y, FIGURE 3 illustrates another arrangement in accordance with this invention whereby the extra core effectively is molded into the multiaperture core-element. Only two cores, corresponding to any odd and even core of a system,

are shown'to simplify the drawing and explanation ofthe transmit aperture of the core 6i and to the receive aper- Y ture @2R of core 62, as well as to the extra aperture 62E of that core. The clear winding 66 is inductively coupledl to the core e2 through both its main aperture and the extra aperture. This assures that the extra aperture.V lis always cleared to a state whereby when current iiows through the transfer winding, it will be driven toward saturation prior to the drive towards saturation of the remainder of the core 62. In this manner, the extra magnetic material subtracts or clips magnetic iux from the'flux being applied to the core 62, and the curve characteristic of the type represented in FIGURE 2 by theV curve 54 is obtained. No interaction between the iiux around the extra aperture with that in the rest of the multiaperture device is intended nor desired. The amount of additional magnetic mateial required for the extra aperture walls is determined by Y the amountof fiux it is desired to subtract from that availl able for driving the core 62 to saturation. T he magnetic material surrounding the receive aperture of the core has a cross-sectional area on either side ofthe aperture at` least equal to half the cross-sectional area of the toroidal arm of the core without an aperture therein, while the cross- Vsectional area of the magnetic material around the extra aperture generally will be smaller than the cross-.sectional areaof the material adjacent the receive aperture, but of Va relative area which is suitable for clipping the desired amount'of liux'linkages transmitted via the transfer loopv to the composite clipper-receiving core.

embodiment of the invention, the necessity forV an extra vaperture in the core is eliminated. The two 'cores 7 1, 72 Vas before have armain aperture EM, 72M, a transmit aperture Tiff, 72T, and a receive aperture 7R,.72R. The transfer winding 74 is: inductively coupled lto both transmit and receive apertures 71T, 72K. A11-,advance Winding 76 is inductively coupled to the transmitfand main apertures 71T, 'HM in `the manner previously described in- FIGURE l.v The clearwindingf is inductivelycoupled to the receive aperture and the main laperture 72M ofthe core7'2.V l Y y,

Assume thatthe cross-sectional areas of the two'legs 9&8?. associated with theV receive aperture 12R areleach larger than half the area of the leg Slof the tor'oid, which V7 exemplifies the portion wherein there is no aperture, Vfor example, one-third larger. Thus, if the area of the leg 84 is A, then legs Si), S2 may be eachV A gil-PK) where K=onethird=the clipping fraction. The amount of the excess corresponds to that required for a saturation flux reversal of, for example, an extra core of the type shown in FIGURE 1. Let the cleared state of the core 84v be as shown, where the arrows indicate the direction of the flux in the cleared state. The outer leg Sii of the input aperture is saturated and the inner leg S2 of the input aperture has two qbc lessux than the outer leg contributing to the total clockwise flux.

It any transfer current flows in the transfer winding in response to ux linkages being switched into the transfer winding from the core 71, it will be found that an amount of ux equal to ec can be switched about the input aperture, at relatively low values of current before any ux yneed be switched about the main aperture of the core 72. Since it is only the flux that is. switched about the main aperture of core '72 that will Vbe available to its output aperture 72T for future transmission to other multiaperture devices, the action of this local switching about the input aperture is essentially equivalen-t to the clipping or robbing action of the extra core shown in FIGURE 1. In other words, the received flux can essentially be interpreted in this case as only that component of the flux which is switched in the outer leg of the input aperture, which switches about the main` aperture. Because of the disparity bet-Ween the switching threshold about 4the two apertures in question, it can be seen that, as ux linkages are being delivered into the input of Vthe core 72, essentially no flux will switch about the main aperture until after NRrpc flux linkages are delivered. This, then, gives the desired action.

In an application by this inventor for Magnetic Logic Device, Serial No. 791,995, 'filed February 9, 1959, and now Patent No. 3,083,355, there is shown an arrangement whereby multiaperture core operations may be simulated, employing cores having a singleV aperture. FIG- URE 5 shows an embodiment of vthis invention applied to an arrangement of the type shown, described, and claimed in that applica-tion. The extra core may be coupled to the transfer winding, where it will provide a transfer characteristic curve of the type shown in FIG- URE 2. It operates in exactly .the same manner as has been described for FIGURE 1. By clipping or providing a flux loss, the S-shaped ux transfer `characteristic curve for the system is enhanced. The arrangement is shown in FIGURE 5. It includes two main toroidal cores 91, 92, an input auxiliary core 911, 921, an output auxiliary core 91T, 92T. The transfer winding y)diV is inductively coupled tothe main apertures of the cores l 91 and 92, Las well as to the main apertures of the cores 91T, 921. Also coupled to the transfer winding in the manner shown in FIGURE 1 is an extra core 96., The

" clear winding 98 will not vonly clear -th'e oddcores (or the even cores, as the case may be) but also will clear i the extra core 96 and the input cores 92I associated with Y flux would beginto switch and thereby deliver iiuxlinkages into the transfer winding. The flux linkages thereby delivered wouldat firstbe absorbed by the extra core 96, Vand then, when this core issaturatedY counterclocltwise,

the remaining iiux linkages would be delivered to core 92. FIGURES 6 and 7 show stillranotherY embodiment of the invention. `This is shown inFIGURE 6 for a directly driven transfer-winding arrangement: and `in FIG- i has the'advance winding coupled thereto.

.URE 7 for a transformer-driven transfer-winding `arrangement. In FIGURE 6 theremay be seen an odd multi- Vaperture core 161 and an even multiaperture core 102,

ing 106 to the center of one side of the transfer winding 104 and from the center `of the opposite side of the transfer winding to the center of one side of the next transfer winding to which the advancing drive is to be app-lied. A direct-drive transfer-winding arrangement is shown and explained in the previously mentioned article by Crane.

In accordance with this invention, an extra core 108 The extra core is driven to saturation by the same current that is applied to the advancing winding to effectuate an advance. The transfer winding 164 is also coupled to the core 108, but

with a sense such that the flux linkages coupled to the transfer winding by the drive yapplied to core 108 opposes those flux linkages sought to lbe transferred via the transfer winding. In other words, the polarity of the voltage induced in the transfer Winding from the extra core 0pposes the flow of current in the transfer winding through the rece-ive aperture 102K of the core 102. The clear winding 110, which clears core 101, also cle-ars core 108.

In FIGURE 7 similar reference numerals are employed for simil-ar functioning apparatus. FIGURE 7 shows how the extra core is coupled to the advance winding 112, which is coupled to the cores 101 and 102 in the same manner as shown in FIGURE 1. After the advance winding 112 has been coupled to the even or second core 162, it is coupled to the extra core 168 in a manner to drive it to saturation. lWhen an advance current flows therethrough, the voltage induced in the ltransfer winding from the extra core being driven opposes and reduces the current flow for a time in the transfer winding. Since the effects of driving core 183 are over before the effects of driving the ,transmit aperture IGIT can terminate, the extra core 103 effectively serves to clip flux linkages at first in the manner described previously where the extra core is driven from the current in the transfer winding instead of positively by the advance current.

The clipper core 108 can Ibe as large in diarneter as 1s desired, since the transfer-.winding current does not affect its switching. Its cross-section of area is adjusted relative to the -number of transfer-loop turns on the extra' core to obtain the desired amount of linx-linkage cllpping.- It is alsoV possible to use a single extra core which is driven in the manner shown in FIGURES 6 and 7 to clip flux or inject negative flux linkages from more than one transfer winding, assuming that all of these transfer loops are being energizedY at the same time. This 1s what happens when a shift is made `from all odd to all even cores or all evento all odd cores. Thus, one extra core is coupled to all the transfer windings coupling even-transmit apertures to odd-receive apertures and one extra core is coupled to all the transfer windings coupling odd-transmit apertures to even-receive apertures.

There has accordingly been described and shown herein a novel and useful arrangement whereby, employing the extra magnetic material, either in the form of a separate toroidal core coupledto a transfer winding, or as a part of the core into which it is sought to transfer the state of remanence of a preceding core, a characteristicY for the encased second core by applying current to a transfer Winding coupling said first and second cores, the improvement comprising magnetic means coupled to said transfer winding for retarding the drive of said second core by `current flowing in said transfer winding until said magnetic means has rst been driven from one state of magnetic remanence to another state of magnetic remanence.

2. In a system of the type wherein it is desired to transfer the state of magnetic remanence of a irst magnetic core to a second magnetic core by applying current to a transfer winding coupling said iirst and second cores the improvement comprising additional magnetic material inductively coupled to said transfer Winding, said additional magnetic material having two states of magnetic remanence and having the property of being drivable from one to the other state of magnetic remanence before said second core can be driven to its state of magnetic remanence lby the current in said transfer Winding.

3. in ya system .as recited in claim 2 Awherein said additional magnetic material comprises a toroidal magnetic core inductively coupled to said transfer winding.

4. In a system as recited in claim 2 wherein said second core has an input aperture through which said transfer winding is threaded and said additional magnetic material is included in said second core adjacent to the magnetic material surrounding the input aperture in said second core, and another aperture in said additional magnetic material through which said transfer Winding is Y threaded.

5. In a system as recited in claim 2 wherein said second core has an input aperture through which said trans- -fer winding is threaded and said additional magnetic material is included in said second core adjacent to the magnetic material surrounding the -input aperture incre-asing the area cross-sectional thereof by at least one-third.

6. A magnetic remanence transfer vsystem including a first and second magnetic core each having two states of magnetic remanence and being drivable from lone to the other thereof, means 'for driving -said second magnetic core to the state of magnetic remanence of said irst magnetic core including a transfer winding inductively coupled to said two cores, means lfor applying transfer 4current directly to said transfer winding, and additional magnetic material having two states of magnetic remanence and being yinduct-ively coupled to `said transfer Winding to be driven yfrom one to the other state of remanence when said second core is driven to a state of 'remanence by current through said transfer winding, said additional magnetic material having the property of 4being drivable to its state of magnetic remanence before .said second magnetic core is driven to its state l@ of magnetic remanence in response to transfer current in said transfer winding.

7. A magnetic remanence transfer system including a first and second magnetic core each having two states of magnetic remanence and `being drivable from one to the other thereof, each core being toroidal in shape and .having a main aperture, a transmit aperture, and a receive aperture, a third ltoroidal core having a main aperture, a closed-loop transfer winding threaded Ithrough said first core transmit aperture, said second core receive aperture and said third core main aperture, and means for applying transfer current -to said closed-loop transfer winding for driving said second core t-o the same state of remanence as said first core, the sense of the transmit winding threaded through said third core being such as to drive it to a state of remanence when said second core is driven to said state of remanence, said third core material being such 'as to enable its bein-g driven to its state of remanence in response to the transfer current before said second core is driven.

8. A magnetic remanence transfer system includ-ing a `first and a second magnetic core each having twoV states of magnetic remanence andbeing drivable from one to the other thereof, each core being substantially t-oroidal in shape and having a main aperture, a transmit aperture, a receive aperture, and an extra aperture spaced from said receive aperture by magnetic material of said core which has .a cross section which is larger than the cross section of said magnetic material between said receive aperture and said main aperture, a closed loop` transfer Winding threaded through said transmit aperture, said extra aperture and said receive aperture, and means for applying transfer current to said closed-loop transfer winding, said closed-loop transfer Winding being threaded through said extra and receive apertures with .a sense .whereby in response to said `transfer current the magnetic material about said extra aperture is drivenv to remanence before the magnetic material about said receive aperture is driven.

Y References Cited in the file of this patent UNITED STATES PATENTS 2,683,819 Rey a July 13, 1954 2,781,503 Saunders Feb. 12, 1957 2,784,390 Kun Li Chien Mar. 5, 1957 2,805,408 Hamilton Sept. 3, 1957 2,935,739 Crane May 3, V1960 3,032,748 Meyer et al. May .1, V1962 3,053,993. Bar-ber Sept. 1l, 1962 3,077,585 Butler Feb. 12, 1963 

7. A MAGNETIC REMANENCE TRANSFER SYSTEM INCLUDING A FIRST AND SECOND MAGNETIC CORE EACH HAVING TWO STATES OF MAGNETIC REMANENCE AND BEING DRIVABLE FROM ONE TO THE OTHER THEREOF, EACH CORE BEING TOROIDAL IN SHAPE AND HAVING A MAIN APERTURE, A TRANSMIT APERTURE, AND A RECEIVE APERTURE, A THIRD TOROIDAL CORE HAVING A MAIN APERTURE, A CLOSED-LOOP TRANSFER WINDING THREADED THROUGH SAID FIRST CORE TRANSMIT APERTURE, SAID SECOND CORE RECEIVE APERTURE AND SAID THIRD CORE MAIN APERTURE, AND MEANS FOR APPLYING TRANSFER CURRENT TO SAID CLOSED-LOOP TRANSFER WINDING FOR DRIVING SAID SECOND CORE TO THE SAME STATE 